Field of the Invention
The present invention relates to a membrane electrode assembly including electrode catalyst layers provided respectively on both surfaces of an electrolyte membrane. Each of the electrode catalyst layers includes polymer electrolyte and catalyst. Further, the present invention relates to a method of producing the membrane electrode assembly.
Description of the Related Art
For example, generally, a solid polymer fuel cell is formed by stacking several tens to several hundreds of unit cells (power generation cells) together, and used as a fuel cell stack, e.g., mounted in a vehicle. Each of the unit cells is formed by sandwiching a membrane electrode assembly (MEA) between a pair of separators.
The membrane electrode assembly includes an electrolyte membrane, an anode facing one side of the electrolyte membrane, and a cathode facing the other surface of the electrolyte membrane. The membrane electrode assembly is a polymer electrolyte membrane. Each of the anode and the cathode includes an electrode catalyst layer facing the electrolyte membrane, and a gas diffusion layer facing the electrode catalyst layer. The electrode catalyst layer includes polymer electrolyte and catalyst, and serves as a reaction field for electrode reaction. A reactant gas is diffused, and supplied through the gas diffusion layer to the electrode catalyst layer.
As a method of producing such a membrane electrode assembly, for example a method using so called the decal method is known as shown in Japanese Laid-Open Patent Publication No. 2010-055922. Specifically, in this production method, catalyst ink is temporarily coated on a film like transfer base material to form a coating film. The coating film is dried, and solvent of the catalyst ink is evaporated to process the coating film into a dried film. Thereafter, the dried film is transferred to the electrolyte membrane to form an electrode catalyst layer.